Plasticized polyvinyl halides



Patented May 8, 1951 PLASTICIZED POLYVINYL HALIDES 7 William S. Emerson and Robert A. Heimsch, Dayton, Ohio, assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application March 25, 1950, Serial No. 151,991

8 Claims. 1.

This invention relates to compositions comprising polymers of vinyl halides and relates more particularly to compositions comprising vinyl chloride polymers plasticized with Z-ethylhexyl esters of certain aromatic dicarboxylic acids.

A wide variety of plasticizers has been employed for the purpose of improving the.physi-' cal properties of vinyl chloride polymers. Particular attention has been given to the improvement of flexibility and heatand light-stability of such plasticized compositions. In many instances the improvement in flexibility has been obtainable only by sacrificing other desirable properties of an ideal polyvinyl chloride composition, such as low volatility, color and heatstability, water absorption, etc.

Now we have found that very good flexibility, without sacrifice of temperature stability and low volatility, is imparted to vinyl chloride polymers when there are employed with the polymers Z-ethylhexyl esters of aromatic dibasic acids having a plurality of benzene nuclei and ether or thioether structures. Esters of this type are disclosed in our copending application, Serial No. 135,301, filed December 27, 1949.

The esters may be represented by the generic k structural formula:

wherein X is an atom selected from the group consisting of oxygen and sulfur atoms, 1!. and m are each small whole numbers from zero to one, inclusive, the sum of m and n is at least one, and R is the radical CH2CH(CE2)3CH3 As illustrative of esters having the above general formula may be mentioned the bis(2-ethy1- hexyl) esters of bis(o-carboxybenzyl) sulfide, of bis(p-carboxybenzyl) ether, of p-carboxybenzyl p-carboxyphenyl sulfide, and of p-carboxybenzyl 4 wherein X is a sulfur or an oxygen atom and n is a small whole number from zero (0) to one (1),

inclusive. The dibasic acids are then precipitated from the aqueous alkaline solution by treatment with a strong mineral acid, and esterified by refluxing with 2-ethylhexanol in the presence of an esterification catalyst.

An alternative procedure for preparing the symmetrical thioether involves the reaction of two moles of the chloromethylbenzoic acid with one mole of an alkali metal sulfide in aqueous alkaline solution, and followed by esterification.

The present esters are valuable plasticizers for polyvinyl chloride and copolymers of at least per cent by weight of vinyl chloride and up to 30 per cent by weight of an unsaturated monomer copolymerized therewith, for example, vinyl acetate, vinylidene chloride, etc. We have found these esters serve not only to soften vinyl chloride polymers, but also to impart simultaneously a-high degree of low temperature flexibility, very good temperature stability and great mechanical strength to these polymers. The present 2-ethylhexyl esters are compatible with vinyl chloride polymers and show no exudation of plasticizer content of up to 50 per cent. Although the quantity of plasticizer will depend upon the particular polymer to be plasticized and upon its molecular weight, it is generally found that compositions having from 5 per cent to 50 per cent by weight of plasticizer will, in most cases, be satisfactory for general utility. The good flexibility of the plasticized compositions increases with increasing plasticizer concentration.

In evaluating plasticizer efiiciency, use is made of the following empirical testing procedures:

C'ompatibiZity.-Visual inspection of the plasticized composition is employed, incompatibility of the plasticizer with the polymer being demonstrated by cloudiness and exudation of the plasticizer.

Hardness.A standard instrument made by the Shore Instrument Company is used for this determination and expresses the hardness in units from 1 to 100. The hardness of a composition is judged by its resistance to the penetration of a 5 standard needle applied to the composition under a standard load for a standard length of time.

Low temperature flexibility-Low temperature flexibility is one of the most important properties of elastomeric vinyl compositions. While many plasticizers will produce flexibile compositions at room temperature the flexibility of these compositions at low temperatures may vary considerably, i. e., plasticized polyvinyl chloride compositions that are flexible at room temperature often become very brittle and useless at low temperatures. Low temperature flexibility tests herein employed are according to the Clash- Berg method. This method determines the torsional flexibility of a plastic at various tempera tures. Thetemperature at which the vinyl composition exhibits an arbitrarily established minimum flexibility is defined as the low temperature flexibility of the composition. This value may also be defined a the lower temperature limit of the plasticized compositions usefulness as an elastomer. V

Volatility.Just as a decrease in temperature often results in decreased flexibility of a plasticized polymer composition so does a decrease in plasticizer concentration when caused by volatilization of the plasticizer. Hence, plasticizers which are readily volatilized from the plasticizedcomposition as a result of aging or heating are inefiicient because upon volatilization the plasticized compositions become stiff and hard. The test for plasticizer volatility herein employed is that described by the American Society for Testing Materials under the designation D-7e4-44T.

Water resistance.The amount of water absorption and the amount of leaching that takes place when the plasticized composition is imme'r'sed in distilled water for 24 hours is deter-'- mined.

The invention is further illustrated, but not limited by the following examples:

Example 1 Sixty parts of. polyvinyl chloride and 40 parts. by weight. of the bis(2 ethylhexyl) ester of bis- (p-carboxybenzyl-l sulfide are mixed on a rolling mill to ahomogenecus blend. During the milling there was observed substantially no turning and discoloration. A molded sheet of the mixture. was clear and transparent and substantially colorless. Testing of the molded sheet for low temperature flexibility, according to the testing procedure described above, gave a value of minus 19' C.., which value denotes good low temperature properties. Tests on the volatility character istics. of the plasticized composition gave a value of 2'.2.per cent which shows very good retention of plasticizer and indicates good temperature characteristics. of the composition. The plastie cizecl material had a hardness of 7'7 before the volatility test. and a hardness of '76v after the volatility test. When subjected to heat at atemperature of 325 F. for a period of 3-3 minutes theclarity and color of the molded product was substantially unchanged. Tests of the waterresistance propertiesof the plasticized material employing the test procedure described above showed a solids-loss of only 0.06 per centand an 0.34 per centwater' absorption value;

Example 2 Operating? as in Example. 1 but employing the bist2-ethylhexyl) ester of p-carboxybenzyl pcarboxyphenyl ether instead of the ester employed in Example 1, there was obtaineda plasticized polyvinyl chloride composition having alow-temperature flexibility value of 1 minus 12 C. Tests on the volatility characteristics-of the plasticized composition gave a'value'oi 1.3 per cent, which value shows very good retention of the plasticizer. The pla'sticized material had a hardness-of 78 before-the volatility test ancl'a' hardness of'77 after the volatility test. When subjected to heat as in Example 1, the color of the presentmolded product was substantially unchanged. Tests of the water-resistance properties-of the present product gave a solids-loss of 0.05per"cent and an-0.29 per cent-water absorption value.

Example 3 Operating as in Example 1, but employing the bis-(2-ethylhexyl) ester of p-carboxylbenzyl pcarboxyphenyl sulfide instead of the ester of Example-l, there was obtained a plasticized polyvinyl-chloride: composition having a low temperature flexibility value of 16 C. Tests on the volatility characteristics of the plasticized composition gave a, value of 1.10 per cent which shows very good retention of plasticizer and indicates good temperature characteristics of the composition. The plasticized material had a hardness of 77 before the volatility test and a hardness of 76 after the volatility test. Tests of thewater-resistance properties of the plasticized material employing the test procedure described above showed asolids-loss of only 9.03 per centand an 0A3 percent water absorption value.

While the above examples. show only a composition in whichthe ratio of plasticizcr to polymer content-is :60, this ratio being employedin order to get comparable efficiencies, the content of ester to polyvinyl chloride may be widelyva-ried, depending upon the properties desired in the final product. For manypurposes a plasticizer content of, say, from only 10 per cent to 20 per cent is preferred. The present esters are compatible with polyvinyl chloride over a wide range off concentrations, up to per cent" of esters based on the. total weightof the plasticized composition yielding desirable products.

Although the invention has been described particularly withreferencc to the use of the pres entlbisQ-ethylhexyll esters of bis(carboxyaryl) chloride, these esters are advantageously employed also as plasticizers for copolymers of vinyl chloride, for example, the copolymers of vinyl chloride with'v-inyl acetate, vinylidene-chloride, methyl methacrylate, acrylonitrile, butadiene, or styrene. have a high vinyl chloride content, i. e., a vinyl chloride content of at least '70 per cent by weight of vinyl chloride and up to 30 per cent by weight of the copolymerizable monomer.

The plasticized polyvinyl halide compositions of thepresentinvention have good thermalstability; however, for many purposesitmay be: advantageous to use known stabilizers in the plasticized compositions. Inasmuch as the present esters are substantially unreaetive with the commercially available heatand light-stabilizers which are commonly employed with polyvinyl chloride or copolymers thereof, the presence of such materials in the plasticized materials does not impair the valuable properties of the present esters. The present esters are of general utility in softening vinyl chloride polymers. They may be-used as theonly plasticizingcomponent in a compounded vinylchloride-polymer or they may beusedinconjunction with other plasticizers.

What we'claim is:

l. A resinous? composition comprising avinyl: chloride polymer pl'asticized with an ester having. the: structure:

0 LOB m) ex -(01mm Preferably,, such copolymers.

inclusive, the sum of m and n is at least one, and R is the radical CH2CH(CH2)3CH3 wherein X is an atom selected from the group consisting of oxygen and sulfur atoms, n and m are each small whole numbers from zero to one, inclusive, the sum of m and n is at least one, and R is the radical OH3CH (CHghCHg 235 said ester being from 5 to 50 per cent of the weight of the composition.

4. A resinous composition comprising a vinyl chloride polymer plasticized with an ester having the structure:

wherein X is an atom selected from the group consisting of oxygen and sulfur atoms, n and m are each small whole numbers from zero to one, inclusive, the sum of m and n is at least one, and R is the radical said ester being from 5 to per cent of the weight of the composition.

, 5. A resinous composition comprising a copolymer of at least per cent by weight of vinyl chloride and up to 30 per cent by weight of an unsaturated monomer copolymerizable therewith, said copolymer being plasticized with an ester having the structure:

wherein X is an atom selected from the group consisting of oxygen and sulfur atoms, n and m are each small whole numbers from zero to one, inclusive, the sum of m and n is at least one, and R is the radical CH2CH(CHZ)3CH3 2H5 and said ester being from 5 to 50 per cent of the weight of the composition.

6. A resinous composition comprising polyvinyl chloride plasticized with the bis(2-ethylhexyl) ester of bis(p-carboxybenzyl) sulfide, said ester being from 5 to 50 per cent of the Weight of the composition.

7. A resinous composition comprising polyvinyl chloride plasticized with the bis(Z-ethylhexyl) ester of p-carboxybenzyl p-carboxyphenyl ether, said ester being from 5 to 50 per cent of the weight of the composition.

8. A resinous composition comprising polyvinyl chloride plasticized with the bis(Z-ethylhexyl) ester of p-carboxybenzyl p-carboxyphenyl sulfide, said ester being from 5 to 50 per cent of the weight of the composition.

WILLIAM S. EMERSON. ROBERT A. HEIMSCI-I.

No references cited, 

1. A RESINOUS COMPOSITION COMPRISING A VINYL CHLORIDE POLYMER PLASTICIZED WITH AN ESTER HAVING THE STRUCTURE: 